GaudiConfig2: strict type checking for list properties

Allow only list (and tuple) types to be assigned to list properties and extend test coverage. This brings GaudiConfig2 in line with the legacy configurables. I.e. the following now fails:

  MyAlg.MyVecOfStrings = "abc"

GaudiConfiguration/python/GaudiConfig2/semantics.py

@@ -360,9 +360,9 @@ class SequenceSemantics(PropertySemantics):
         self.value_semantics.name = "{} element".format(self._name)
 
     def store(self, value):
-        if not isinstance(value, (list, _ListHelper)):
+        if not isinstance(value, (list, _ListHelper, tuple)):
             raise TypeError(
-                "list expected, got {!r} in assignment to {}".format(value, self.name)
+                "list or tuple expected, got {!r} in assignment to {}".format(value, self.name)
             )
         new_value = _ListHelper(self.value_semantics)
         new_value.extend(value)